We know that the 3+1 dimensions all fit together in a nicely with Lorentz covariance. We can rotate and apply Lorentz boosts without breaking the laws of physics. How do string theory's extra dimensions fit in with this? Does it make sense to rotate between a normal space dimension and one of these "extra" dimensions, or between two extra dimensions? In relativity, a 4-vector is something special. Do we have to go to a 10-vector in 10D theory? Or are all these extra dimensions not part of the same "space-time"? Are there additional symmetries and conserved quantities associated with these dimensions? Sorry--that's a lot of questions at once.